The present invention relates to a method and devices for machining various materials using a laser beam.
As the reduction in size (miniaturization, high-definition, or the like) of various products progresses, the demand for a high definition and high precision machining technique is mounting. Moreover, the manufacturing processes have been diversified along with the transition of products market trends and the variety of materials used there is also expanding. With such diversified demands, it is becoming challenging to manage them with conventional techniques, such as mechanical machining and photolithography. Today laser-machining technique is looked on as powerful means to meet such demands finding a number of applications in broad industrial fields.
In laser-machining, when using a laser beam whose energy intensity distribution is a Gaussian distribution, there will be differences in the machining conditions of the material due to the non-uniformity of the energy intensity between the center of the beam and the periphery (in the outer side) thereof, thus a uniform machining hardly takes place. In order to avoid such an inconvenience, the process margin for the irradiating condition of the laser beam will be narrowed, and thus manufacturing process will be unreliable, or the option for the materials to serve as a machined object will be restricted significantly. On the other hand, it is known that the quality of the machining can be improved by adopting a laser beam whose energy intensity distribution is made to be an almost flat distribution (a top hat distribution) (For example, refer to the following Patent Document).
Japanese Unexamined Patent Publication No. H8-33993 is an example of the related art.
In the laser-machining using the above-described conventional technique, the energy intensity distribution of the laser beam is shaped into a top hat-like shape by letting the vicinity of the peak intensity of the laser beam partially pass through an amplitude mask. For this reason, some part of the laser beam outputted from a laser oscillator results in being truncated, and thus the efficiency in use of light is low. Moreover, in the conventional technique described above, the diffracted beams with the orders of a limited range (for example, up to ±3rd order) are imaged by letting the laser beam pass through an aperture of the mask, and thereby the top hat-like energy intensity distribution is realized. For this beam-shaping mechanism some ripples will occur in the distribution due to the truncation of the diffracted beams with higher orders, and thus the uniformity of the energy intensity distribution of the shaped laser beam is not sufficient.
An advantage of the invention is to provide a technique allowing for a significant improvement of the efficiency in use of light when machining with a laser beam having a top hat intensity distribution.
Another advantage of the invention is to provide a technique enabling improvement of the uniformity in the energy intensity distribution of the laser beam when machining with a laser beam having a top hat intensity distribution.